The long range goal of the proposed research is to develop high resolution quantitative imaging of single photon emitters. Specifically, the aim is to complete the design, fabrication, and evaluation of a Single Photon Ring Tomograph (SPRINT) for the measurement of radiopharmaceutical distribution studies and kinetics. SPRINT utilizes an interchangeable coded ring aperture, and the proposed work includes a study of optimal codes, Z-axis collimation design, and implementation of both analytic and experimental methods of attenuation correction. Iterative image reconstruction algorithms will be employed and special purpose computer hardware will be designed and built to accomplish the reconstruction at very high speed.